1. Field
This disclosure relates generally to semiconductor fabrication, and more specifically, to a mechanism for visibly identifying on each device die of a wafer.
2. Related Art
There are many well-known semiconductor processing techniques for manufacturing modern integrated circuits. A typical procedure in the manufacturing process includes photolithography, which involves passing light through a reticle, or mask, to expose a layers image for one or more die on a wafer. The wafer is moved to a new position (a process called “stepping”) and the photolithographic processes are repeated until the pattern of the reticle has been replicated on each die of the wafer.
A drawback of such a conventional photolithographic process is that it is not possible to provide a unique identification for each die on the wafer. This is because the same reticle is exposed in multiple locations and results in the same pattern at each location. But the ability to uniquely identify each die from a wafer, even after the die have been separated from the wafer, can provide certain advantages such as tracking of the die during and after test, assembly, and packaging processes. It is therefore desirable to provide a mechanism by which each die from a wafer can be uniquely identified. It is further desirable that the identification mechanism have minimal impact on overall device processing steps, as well as provide no increase in radio frequency interference on the device die.
The use of the same reference symbols in different drawings indicates identical items unless otherwise noted. The figures are not necessarily drawn to scale.